1. Field of the Invention
The invention relates to an impeller for a pump, especially for a cooling water pump of an internal combustion engine, comprising a hub, a cover disk which is disposed on the intake side and is provided with a central opening for sucking in a conveyed medium, and with a blade which is joined integrally with the cover disk on the intake side and is provided with an inner section located in the region of the central opening and an outer section located in the region of the cover disk.
2. The Prior Art
The impellers of radial pumps are used as cooling water pumps of motor vehicles, for example, are predominantly configured as so-called closed impellers. This means that blades are enclosed between two cover disks, as a result of which closed flow conduits are formed with the impeller. Such closed impellers allow achieving high pumping efficiencies. The disadvantageous aspect is, however, that the production of such impellers is complex. Such a production can occur, for example, in two-part form in such a way that, on the one hand, a cover disk is produced with blades formed thereon, and on the other hand, the other cover disk is produced separately from one another and are joined to form the final impeller. Such a solution is shown in U.S. Pat. No. 2,710,580 A. It is also possible to produce such an impeller in an integral way in a casting method. A complex multi-part casting mold is required for this purpose which is provided with a plurality of slides which shape the flow conduits.
In order to enable the configuration of such an impeller in a simple and cost-effective way, it is desirable to design an impeller which can be produced with a simple two-part casting mold. DE 40 40 200 A shows such a solution in which the impeller comprises a cover disk on the pressure side and a cover disk on the intake side, between which the blades are arranged. The cover disk on the intake side comprises a central opening whose internal diameter is larger than the outside diameter of the disk on the pressure side. Insofar as the blades are configured without undercuts, such an impeller can be produced in a two-part form because the removal from the mold is easily possible. The disadvantageous aspect in such an impeller is however that the efficiency is relatively low and substantially lower than in the closed impellers as a result of the mandatory geometrical conditions. There is a further easy to produce solution with an impeller with plain blades and a respectively lower efficiency. The predominant aspect in the function is the rotation in both directions.
It is known to improve the pumping efficiency of radial pumps or axial pumps by using three-dimensionally curved blades. Such a solution is described for example in DE 100 50 108 A. The production of such impellers is very difficult and is not suitable for mass production for reasons of cost effectiveness and process technology. DE 197 42 023 A discloses an impeller composed of several segments in which the individual parts are easy to produce, but in total are complex and therefore difficult to produce. A further impeller with totally three-dimensionally curved blades is described in JP 59165895 A. The production is also complex in this case too.
It is the object of the present invention to provide an impeller for a pump which avoids these disadvantages and combines the advantage of easy production with high efficiency.